Thermostatic regulator for electric heating elements



May 23, 1950 BELGER] 2,508,349

THERMOSTATIC REGULATOR FOR ELECTRIC HEATING ELEMENTS Filed Feb. 1'7, 1948 Patented May 23, 1950' THERMOSTATIC REGULATOR FOR ELECTRIC HEATING ELEMENTS Paul Beleri, Geneva, Switzerland, assignor to Brevets et procds Pyror S. A., Geneva, Switlerland, a corporation of Switzerland Application February 1'1, 1948, Serial No. 8,987 In Switzerland February 21, 1947 4 Claims.

This invention relates to a thermostatic regulator for electric heating bodies, in which the deformations of a thermocouple are used to operate at least one mercury switch controlling the circuit of the said heating body. The regulator is characterized in that the said switch is mounted on an oscillating member the movement of which is controlled by the deformations of the thermostat by means of a flexible connection whose active length is adjustable for the purpose of modifying the period of time intervals between the periodic closing and opening of the said switch.

The accompanying drawing shows, by way of example, an embodiment of the regulator according to the invention.

Fig. 1 is a diagrammatic view of this embodiment, and

Fig. 2 is a diagram showing two adjustments of the temperature of the working apparatus.

The object of the regulator according to the invention is to control a heating power (such as that of an electric heating body) by periodic interruptions of the current, the alternating periods of interruption and.operation being automatically determined by the deformations of a thermostatic member such as a bi-metallic member, for example, having a winding inserted in the controlled circuit (for example the circuit of the heating element). I indicates a general hand operated switch, inserted between a terminal D of a current supply from the network, for instance, and the heating element of a heating apparatus shown as an electric resistance 2. The regulator proper 3 includes a mercury switch 4 the electrodes of which 5 and 6 are respectively connected to the terminal E of the network and to the heating resistance 2. This switch 4 bears on two bearings I'I mounted on a support I capable of oscillating about an axis 8 pertaining to the frame of the regulator 3. A spring 9 tends to retain the support I in its normal position corresponding to the closing of the switch 4 through the mercury. The movement of the support 'I is controlled by the deformations of a bi-metallic member I0 by means of a flexible connection II the length of which is adjustable. One end of this connection II is secured to the oscillating support 1 and the other end to a rotatable member I2, for example a drum or a rod, about which it is adjustably wound in order to vary its active length, the intermediate part of this connection passing round a pulley I3 integral with the movable end of the bi-metallic element Ill. The flexible connection II might also slide in a groove integral with the movable end of the element It. The other end of the element III is secured to a stand I4 integral with the frame of the regulator 3. The rotatable member I2 is hand operated by means of a knob I5 provided with a scale It moving in front of a fixed guide mark I'I. Inverseiy, the guide mark might be movable and the scale fixed.

Although in the regulator described, the heating resistance I0 of the element It is connected in parallel with the heating resistance 2 of the apparatus to be controlled, it could also be connected in series with this resistance 2 which would thus vary the control of the intensity of heating as will hereinafter be described.

The operation of the regulator described is as follows:

Supposing the switch I to be closed, the current flows, for example from D to E passing through the heating resistance '2, the resistance I0 for heating the bi-metallic element I0 and the mercury connecting the electrodes 5 and 6. The movable end of the element It moves under the effect of heat produced by the passage of the current through resistance I0 and, by means of the pulley I3, exerts a pull on the connection II. This pull, acting in opposition to the spring 9, causes the support I to oscillate thus bringing about the breaking of the circuit between the electrodes 5 and 6 and, consequently, the interruption of the current through resistances 2 and III.

If a rapid action of the bi-metallic element on the oscillating support I is desired, the connection I I will be wound round the member I2 by means of the knob I5 so as to change the position of rest of the support I. The initial deformations of the element It! will then require a very short time before acting on the oscillating support I of the switch 4. On the other hand, if the connection II is unwound by turning the knob IS in a contrary direction, the initial deformations of the element It! will first of all serve to stretch the connection II and will therefore take a certain time before acting on the support I.

Moreover, any other mechanical means might be resorted to in order to produce a variation in tension of the flexible connection II by turning the knob I5.

It will be noted that the control realized by the regulator described (expressed in percentage of the heating power) is not a function directly proportional to the angular displacements of the adjusting knob I5.

In the diagram shown in Fig. 2, the ordinates 3 correspond to the percentage of the heating power and the abscissae to the angular displacements oi the adjusting knob 15.

The curve A shows, for example, that the heating of the working apparatus increases slowly at the outset and more rapidly towards the end of the angular displacement of the knob Ii. The adjustment is therefore more sensible at low intenslties, which is of importance in case the intensity of the source of heat must be that corresponding to the simmering of a dish, for example. On the other hand, this advantage is turned into a disadvantage ii the intensity of the source of heat must be that of an oven. In this case, the shape of the curve must be similar to that of curve B (Fig. 2) that is to say that the adjustment must be more sensible at the upper part of the curve. The intersecting point C of the curves A and B corresponds to 100% of the heating power.

By connecting the heating resistance of the bi-metallic element in series with the heating resistance 2 of the working apparatus, the control shown by the curve B is realized and by connecting this resistance ID in parallel with the resistance 2, the control realized is the one shown by the curve A.

What I claim is:

l. A thermostatic regulator comprising a support oscillatably mounted, a, two-electrode mercury switch mounted on said support, means normally holding said support in a normal position whereby said mercury switch is in closed position, a bi-metallic element, energizing means for said element, a flexible connection between said element and said oscillatable support, manual means for varying the length of said flexible connection, said flexible connection being operated by said element to oscillate said support and said switch against action of said holding means for making and breaking contact in said switch, the length 0! said connection regulating the frequency of aperation of said switch.

2. In a, thermostatic regulator as claimed in claim 1, an end of said flexible connection being secured to said oscillatable support, a rotatable member, the opposite end of said flexible connection being wound about said rotatable member, the amount of said connection wound on said rotatable member being adjustable to vary the length of said connection, and an intermediate portion oi said connection cooperating with a tree movable end of said bi-metallic element.

3. In a thermostatic regulator as claimed in claim 2, a holding member secured to the tree movable end of said bi-metallic element, said intermediate portion 01 said flexible connection slidably engaging said holding member.

4. In a thermostatic regulator as claimed in claim 3, said holding member consisting of a pulley, said intermediate portion of said connection passing around said pulley.

PAUL BELGERI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,651,629 Phelan Dec. 6, 1927 1,928,907 Noble Oct. 3, 1933 2,012,428 Hollinshead Aug. 27, 1935 2,088,728 Stranszky Aug. 3, 1937 2,224,596 Desfachelles Dec. 10, 1940 

